The Mechanisms Study Of LncRNA MT1JP Involved In The Development And Progression Of Gastric Cancer

Gastric cancer is one of the most common malignant tumors with the third mortality rate of cancer in the world. In China, the morbidity and mortality of gastric cancer ranks high on the list of malignant tumours. New onset cases are more than 400,000 each year. There are no symptoms or mild symptoms in the early stages of gastric cancer. Because of lacking early diagnostic biomarkers, it’s too late to miss the best treatment time. Surgical resection and chemoradiation are the main treatments in gastric cancer. But 5 years survival rate of gastric cancer is only 40% because of frequent recurrence. Therefore, gastric cancer brings serious harm to patients and the society. Now, there are many studies on biological characteristics of gastric cancer. Due to the absence of diagnostic biomarkers, prognostic indicators and effective therapeutic targets, it has always been a bottle neck in the treatment of gastric cancer. Studies on the mechanism of the development of gastric cancer are very important. The more markers with potential prognostic should be found to improve the quality of life of patients with gastric cancer.The occurrence of gastric cancer is the result of the interaction of environmental and genetic factors. Environmental risk factors include dietary factors such as high dose in take of salt, occupational exposure, helicobacter pylori infection, smoking, drinking and soon. However, people are in the same condition of environmental factors, only a few have finally developed into gastric cancer which indicates that the genetic factors are of great importance. A large number of researches show that genetic factors play an important role in the development of gastric cancer. These researches mainly focus on protein coding genes. The mutations of these genes let to abnormal biological function. With the further research of molecular genetic mechanism, people found that the epigenetic gene also plays an important role in the occurrence and development of gastric cancer. The epigenetic mechanism mainly includes:histone modification, chromatin remodeling, DNA methylation and non coding RNA. The protein coding genes accounted for only 2% of the total transcription gene. Most of the genes are transcribed into nonprotein coding RNA. According to the different lengths of non coding RNA, it can be classified into two groups. One is small RNA including microRNA(miRNAs), small interfering RNA (siRNAs) and Piwi RNA (piRNAs). The function and regulation mechanism of the small RNA have been widely studied. Another is long non-coding RNA (IncRNA) which was initially regarded as "transcriptional noise", without biological function. However more and more evidences have indicate that 1ncRNAs can regulate the gene expression through the transcription, post transcription and epigenetic levels including cancer invasion and metastasis, cell differentiation and apoptosis. With the increase of the researches on 1ncRNAs, more and more 1ncRNAs are found in avariety of tumors including gastric cancer. However researches of 1ncRNAs are still in initial stage in gastric cancer. The mechanisms of lncRNAs in the pathogenesis of gastric cancer remainings unclear.In this study, by using of high-throughput screening and qRT-PCR, we try to identify abnormal expression 1ncRNAs in gastric cancer and conduct a series of molecular biology experiments to clarify their role in carcinogenesis and the possible molecular mechanisms and to provide important reference for the individualized prevention, early intervention and diagnosis of gastric cancers.Part Ⅰ The expression and clinical value of lncRNA MT1JP in gastric cancerBackground:Gastric cancer is one of the most common malignant tumors in digestive system. In China, the incidence and mortality of gastric cancer ranked the second in all tumors. The progression of gastric cancer is a stepwise process with multiple genes and factors. Epigenetic factors act an important role in the occurrence and development of gastric cancer. Recent studies showed IncRNA were involved in the regulation of gene expression at the transcriptional, post transcriptional and translational level. In this study, we found 1ncRNAs played a key role in gastric cancer progression. However, the mechanism is not clear.Methods and Results:LncRNA microarray screening of 5 pairs of gastric cancer tissues and adjacent nontumor tissues were performed. And then we integrated GEO GSE53137 IncRNA expression profile chip data of gastric cancer. Finally, we found the lncRNA MT1JP had a significantly lower expression in cancer tissues compare adjacent nontumor tissues. Furthermore, The assay of validation sample and TCGA data confirmed mis finding. The expression of lncRNA MTlJP was mainly concentrated in the cytoplasm and was related to grading staging and lymph node metastasis based on the correlation analysis and clinical phenotype. Among gastric cancer patients, the lower expression lncRNA MTlJP increased risk of death by 33% than gastric cancer patients with high expression of 1ncRNAMT1JP.Conclusion:We identified a novel IncRNA MT1JP which was significantly decreased in gastric cancer tissues. And IncRNA MT1JP could participate in the gastric cancer progression (lymphatic metastasis, clinical stage) and prognosis. The results of this study not only provide clues for novel clinical biomarkers to evaluation of gastric cancer progression and evaluating potential prognosis, but also provide theoretical basis for the further mechanisms study of IncRNA MT1JP involved in the development and progression of gastric cancer.Part Ⅱ Molecular mechanisms of lncRNA MT1JP in regulation the occurrence And development of gastric cancerBackground:In the past, lncRNA was thought to be non functional sequence of coding protein ability. However, more and more researcher found that lncRNAs play a biological function in influencing tumor cell proliferation, apoptosis, invasion and metastasis in transcription, post transcription and translation levels. The competitive endogenous RNA hypothesis proposes that transcripts with shared microRNA binding sites compete for post-transcriptional control. This hypothesis has gained substantial attention as a unifying function for long non-coding RNAs, pseudogene transcripts and circular RNAs.Methods and Results:LncRNA MT1JP overexpression vector was constructed and then transfected into gastric cancer cells. Further CCK-8, transwell, and flow cytometry detect that lncRNA MT1JP exerted an evident inhibition role on proliferation, migration and invasion and promote apoptosis. Overexpression of lncRNA MT1JP can significantly inhibit the ability of gastric cancer cells to form tumor in vivo. The bioinformatics analysis indicated that lncRNA MT1JP with high abundance in the cytoplasm may act as "competition endogenous RNA (ceRNA)". By combining molecular cell biology experiments of the reporter gene, cell overexpression or interference and Western blot, we found that lncRNA MT1JP may regulate FBXW7 competitive binding miRNA-92a-3p involved in the occurrence and development of gastric cancer.Conclusion:We identified a novel IncRNA MT1JP, which could inhibit proliferation, migration and invasion and promote apoptosis. LncRNA MT1JP may regulate FBXW7 competitive binding miRNA-92a-3p involved in the occurrence and development of gastric cancer. The results of this study not only explain the role of IncRNA in the development of gastric cancer, but also provide important ideas and clues for the study of genetic regulation mechanism in gastric cancer.